New data are presented for the shear behavior of solutions of polyisobutylene in toluene at 25°C. Five samples (viscosity‐average molecular weight range of105to5×106) were studied at shear rates from 1.0 to3×105 sec−1.Both Couette and capillary viscometers were used in the investigation. The results are correlated by a standard reduced variable plot and compared with earlier data. A method for predicting the viscosity of straight chain polymer solutions from minimal data is discussed.